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This undated booking photo provided by the Chickasaw County Sheriff's Office in New Hampton, Iowa, shows Zachary Koehn, who was charged Koehn with murder in the death of his 4-month-old son, whose maggot-infested body was found in a baby swing in the family's home.

A prosecutor in the trial of an Iowa father whose infant son was found dead in a baby swing last year has told a jury the child "died of diaper rash."

Assistant Iowa Attorney General Coleman McAllister told jurors Tuesday that 4-month-old Sterling Koehn had been in the same diaper for nine to 14 days when his body was found in the swing Aug. 30, 2017, at his parents' Alta Vista apartment, the Courier reported.

The baby's father, 29-year-old Zachary Paul Koehn, is charged with murder and child endangerment. The boy's mother, Cheyanne Harris, is also charged and faces a separate trial at a later date.

McAllister said Tuesday in opening statements that the baby's heavily soiled diaper attracted bugs. The resulting diaper rash led to ruptured skin, and e.Coli bacteria set in.

McAllister denied the defense's claims, saying Koehn was an experienced parent. He noted that Koehn's 2-year-old daughter was also in the apartment and was healthy, and that Koehn had money to buy food and baby supplies. He stated Koehn was a drug user.

Nurse and county rescue squad EMT Toni Friedrich testified Tuesday that she was the first to arrive at the apartment after Koehn called 911 to report the baby had died. Friedrich said Koehn showed no emotion when he led her to the dark, hot bedroom where the baby's body was.